linux-kernel - [PATCH] nfs: Annotate struct nfs_cache_array with __counted

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Message-ID: <20240814100128.157057-1-thorsten.blum@toblux.com>
Date: Wed, 14 Aug 2024 12:01:28 +0200
From: Thorsten Blum <thorsten.blum@...lux.com>
To: trondmy@...nel.org,
	anna@...nel.org,
	kees@...nel.org,
	gustavoars@...nel.org
Cc: linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	Thorsten Blum <thorsten.blum@...lux.com>
Subject: [PATCH] nfs: Annotate struct nfs_cache_array with __counted_by()

Add the __counted_by compiler attribute to the flexible array member
array to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

Increment size before adding a new struct to the array.

Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
---
 fs/nfs/dir.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 4cb97ef41350..492cffd9d3d8 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -151,7 +151,7 @@ struct nfs_cache_array {
 	unsigned char folio_full : 1,
 		      folio_is_eof : 1,
 		      cookies_are_ordered : 1;
-	struct nfs_cache_array_entry array[];
+	struct nfs_cache_array_entry array[] __counted_by(size);
 };
 
 struct nfs_readdir_descriptor {
@@ -328,7 +328,8 @@ static int nfs_readdir_folio_array_append(struct folio *folio,
 		goto out;
 	}
 
-	cache_entry = &array->array[array->size];
+	array->size++;
+	cache_entry = &array->array[array->size - 1];
 	cache_entry->cookie = array->last_cookie;
 	cache_entry->ino = entry->ino;
 	cache_entry->d_type = entry->d_type;
@@ -337,7 +338,6 @@ static int nfs_readdir_folio_array_append(struct folio *folio,
 	array->last_cookie = entry->cookie;
 	if (array->last_cookie <= cache_entry->cookie)
 		array->cookies_are_ordered = 0;
-	array->size++;
 	if (entry->eof != 0)
 		nfs_readdir_array_set_eof(array);
 out:
-- 
2.46.0